I use a different approach to dream interpretation. I think the symbols in dreams themselves have meaning specific to the dreamer. So everything, and everyone in the dream is an unconscious representation of some aspect of the dreamer. You are dreaming about it now to help resolve some important issue, propel you towards forward growth, and/or acknowledge a current obstacle in your life that you may not be aware of (or in denial about), like stress. Bad, or scary dreams, seem to me to be mostly stress related. If you can recall your dreams it helps to pay attention to them. Especially recurrent dreams. They seem to be a particularly meaningful message that your unconscious wants your conscious (daily awareness) mind to get. You'll find that once you figure these dreams out, your repeating dream will "move on" to deliver the next message.
So I do believe that teeth falling out in dreams (or any dream symbols) are most successfully interpreted within the context of the individual's life, including their relationships, goals, stresses, culture, and day-to-day life circumstance. You may wonder, "Michael, why don't you write a book on dreams." Well, believe it or not, I didn't exactly come up with this on my own. Fritz Perls and other Gestalt Psychology theorists laid the groundwork for this type of dream interpretation. I like it. I use it often in my practice, and have had success with it. Try it. It works best when you have someone who knows you, and whom you trust (No, it doesn't have to be a therapist) to help you with it.